The present invention refers to a method for detecting a discontinuity in the electrical connections of a microchip and circuit using said method.
The present invention in particular refers to a power voltage device, having the means needed for detecting a discontinuity in the electrical connections during an in-package control phase.
The so-called wire bonding technology uses various process typologies and is currently the most common technique used for making electrical interconnections between the semiconductor chip and the printed circuit.
In addition, the wire bonding technology is fundamental for ensuring that the power arrives at the input of the semiconductor chip and that the information is placed on the outputs of the printed circuit.
With reference to FIG. 1, the wire bonding process for a ball bonding type connection comprises a first phase of ball bonding for a first connection pad 1 of a semiconductor chip 2 and a second bonding phase for a second connection pad 3 of a printed circuit 4.
As shown by FIG. 1, after making the first ball bonding phase, a wire 5 is guided by the second connection pad 3 of the printed circuit 4 by means of a capillary 6 to the first connection pad 1.
At the end of the production process the device is submitted to various control and verification tests of the electrical performance and the quality of the electrical connections.
Nevertheless the current test circuits do not detect unequivocally the discontinuities of the connection wires.
In fact, the device can result valid even after the connection wires have been checked in the event that all the electrical parameters characterizing the device itself remain within the minimum and maximum design thresholds.
Normally the discontinuity of the connections happens when resin is injected under pressure in the semiconductor package 2.
As a consequence, when the device is used in working conditions, there are evident reliability problems.
In addition, the number of input and output terminals keeps growing as the density of integration of the integrated devices increases, and this entails a greater risk of discontinuity in the connection wires.
Therefore all this causes an increase in the possible discontinuities in the connection wires leading to a production of less reliable devices.
For example, in the case of power voltage regulator devices, so that they operate well, said power voltage circuit has to be designed as much balanced as possible, so as to improve both the resistance to thermal peaks and the so-called SOA (Safe Operating Area).
To obtain adequate balancing precise resistive ballast and a precise arrangement of the input and output pads has to be adopted.
In fact, in power voltage regulator devices a correct configuration of the input and/output pads has to be observed.
In addition, it has to be remembered that in said devices only one pad is present for one input voltage for a signal, that is Vin pad, and only one pad for an output voltage of a signal, that is Vout.
The current control or test circuits are not capable of selecting devices in package, such as, power voltage regulators, in which one single pad is present, that is, there is only one pin.
In fact it could happen that the device passes the control test even if it has an electrical discontinuity.
In view of the state of the technique described, the object of the present invention is to supply a method that is capable of preventing a device from being claimed definitely valid after a reliability test.
A further purpose of the present invention is to make a circuit that is capable of unequivocally identifying the electrical discontinuity.
According to the present invention, said object is reached by means of a method for detecting a discontinuity in the electrical connections of a microchip comprising a voltage supply line, a plurality of circuit sections of said printed circuit, an input pin connected to said voltage supply line, an output voltage line, able to connect said plurality of circuit sections to an output pin and a resistive divider made up of a plurality of resistances, characterized in that it comprises the following succession of steps: a) to determine the number of connections in function of the short circuit current both for said input pin and for said output pin; b) to section said voltage supply line in function of the number of the electrical connections determined at point (a) for said input pin; c) to connect the sections of said voltage supply line independently, by means of a plurality of connection wires, with a respective plurality of sections of said printed circuit; d) to section an output voltage line in function of the number of electrical connections determined at point (a) for said output pin; e) to increase in function of the number of electrical connections determined at point (a) the number and the value of the resistances constituting said output divider.
This purpose is also reached by means of a power voltage circuit comprising a voltage supply line, able to supply a plurality of circuit sections of said printed circuit, an input pin connected to said voltage supply line, an output voltage line, able to connect said plurality of circuit sections to an output pin and a resistive divider made up of a plurality of resistances, characterized in that it comprises an equal plurality of connection wires, between said input pin and said circuit sections and between said output pin and said circuit sections.
Thanks to the present invention a method can be made by means of which there is no longer any uncertainty regarding the reliability of the device checked.
Thanks to the present invention a power voltage device can be made which is capable of unequivocally detecting the presence of a discontinuity in the electrical connections.